The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 26, 1993
Filed:
Nov. 16, 1992
Matsushita Electric Works, Ltd., Osaka, JP;
Abstract
An electrode of a discharge lamp which has an improved adhesion between an emitter material and a filament is formed in accordance with the following method. That is, a Fe-Cr-Al alloy is used as the filament. The filament is placed in a heated oxidizing environment to precipitate an aluminum oxide layer uniformly in a surface thereof. Thus precipitated aluminum oxide layer has good adhesion with the filament without flaking thereof. The aluminum oxide layer is coated with triple carbonates consisting of barium carbonate, calcium carbonate and strontium carbonate, so that a carbonate coated filament is obtained. And then, the coated filament is heated in vacuum to reduce the carbonates to their alkaline earth oxides of the emitter material, and also to form a complex oxide consisting of the aluminum oxide and the alkaline earth oxides. Adhesion between the emitter material and the aluminum oxide layer is improved by the formation of the complex oxide, so that a lamp life of the discharge lamp is remarkably increased. On the other hand, since the Fe-Cr-Al alloy has a much higher specific resistance value than tungsten, the discharge lamp using the filament of the Fe-Cr-Al alloy can be operated by a small current, which in turn enables a lamp driving circuit to be reduced in size and weight.